At least two different monomers can be polymerized in the same polymerization system so as to generate a copolymer having those different monomer units arranged as repeating units in one polymer chain, and the copolymer thus obtained can be classified into a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer, depending on the arrangement of the monomer units. However, no report has been made on the arrangement of monomer units in polymerization reaction of a conjugated diene compound and a non-conjugated olefin.
For example, JP 2000-154210 A (PTL 1) discloses a catalyst for polymerization of a conjugated diene, the catalyst including a group IV transition metal compound which has a cyclopentadiene ring structure, in which an α-olefin such as ethylene is exemplified as a monomer copolymerizable with the conjugated diene. However, no reference is made on the arrangement of monomer units in the copolymer. Further, JP 2006-249442 A (PTL 2) discloses a copolymer of an α-olefin and a conjugated diene compound, but no reference is made on the arrangement of monomer units in the copolymer. Further, JP 2006-503141 A (PTL 3) discloses an ethylene-butadiene copolymer synthesized by using a catalytic system consisting of a specific organometallic complex, but merely describes that the butadiene as a monomer is inserted in the form of trans-1,2-cyclohexane into the copolymer, without making any reference to the arrangement of monomer units in the copolymer, and no reference is made to defining the length (molecular weight) of a unit derived from a non-conjugated olefin in the block copolymer of a conjugated diene compound and a non-conjugated olefin so as to manufacture a rubber that is excellent in fatigue resistance, low-heat generation, and elongation at break.
In addition, JP 11-228743 A (PTL 4) discloses an unsaturated elastomer composition composed of an unsaturated olefin-based copolymer as a random copolymer and a rubber. However, it is merely described that monomer units in the copolymer are randomly arranged, and no reference is made to defining the length (molecular weight) of a unit derived from a non-conjugated olefin in the block copolymer of a conjugated diene compound and a non-conjugated olefin so as to manufacture a rubber that is excellent in fatigue resistance, low-heat generation, and elongation at break.
Further, JP 2000-86857 A (PTL 5) discloses a butadiene copolymer in which: a vinyl bond content (vinyl bond content, the content of 1,2 adducts (including 3,4 adducts)) is 6%; a cis content is 92%; and an ethylene content is 3% or 9%. However, the length (molecular weight) of a unit derived from ethylene in the copolymer is large, and thus, due to the crystallinity of ethylene, the physical property of the copolymer becomes similar to plastics in terms of physical property, leading a problem that fatigue resistance (bending and elongation test resistance) and elongation at break are impaired.
In addition, JP 2000-86857 A gives no reference or suggestion to defining the length (molecular weight) of a unit derived from a non-conjugated olefin in the block copolymer of a conjugated diene compound and a non-conjugated olefin so as to manufacture a rubber that is excellent in fatigue resistance, low-heat generation, and elongation at break.